This invention relates to the performance analysis of combustion chambers in a gas turbine. In particular, the invention relates to a computer software application for analyzing temperature differences between exhaust thermocouples which correspond to specific combustion chambers in an operating gas turbine.
As shown in FIG. 1, a gas turbine 10 has a combustion section 12 in a gas flow path between a compressor 14 and a turbine 16. The combustion section may include an annular array of combustion chambers 20, e.g., combustion cans. The turbine is coupled to rotationally drive the compressor and a power output drive shaft 18. Air enters the gas turbine and passes through the compressor. High pressure air from the compressor enters the combustion section where it is mixed with fuel and burned. High energy combustion gases exit the combustion section to power the turbine which, in turn, drives the compressor and the output power shaft 18. The combustion gases exit the turbine through the exhaust duct 19, which may include a heat recapture section to apply exhaust heat to preheat the inlet air to the compressor.
The combustion gases swirl partially around the axial centerline of the gas turbine, as the gases move axially through the turbine. This swirl of the combustion gases is due to the rotation of the turbine blades and of the compressor blades. The amount of swirl in the combustion gases between the combustion section 12 and exhaust ducts 19 depends on the operating condition of the gas turbine, such as its stage load, duty cycle, ambient temperature and other factors. When the combustion gases exit the exhaust duct, the gases have swirled about the axis of the gas turbine and are not axially aligned with the combustion chambers 20 that generated the gases.
A liquid and/or gaseous fuel supply 22, including piping, valves and controls, distributes fuel to each combustion chamber 20. The fuel flows to a fuel nozzles 24 at an upstream end of each of the chambers. Fuel is injected via the nozzles 24 into each chamber and mixes with compressed air flowing from the compressor. A combustion reaction of compressed air and fuel occurs in each chamber.
It is generally preferable to have uniform combustion reactions, e.g., at the same temperature, in each of the chambers. A uniform flow of combustion gases, e.g., common temperature, from all combustion chambers is desirable for optimal combustion performance and for uniformly powering the turbine 16. Hot combustion gases flow from the array of combustion chambers 20 to the rotating turbine 16. The combustion gases flowing from each individual combustion chamber mix with combustion gases exiting the other chambers to form a combined stream of hot gases exiting the turbine exhaust duct.
Non-uniformity in the flow of combustion gases, e.g., an excessively-hot or cold section of the gas flow, is indicative of a problem in the combustion section. Identifying a non-uniformity in the gas flow in the combustion section is difficult. The uniform flow of combustion gases and the swirling of gases from the different chambers effectively masks combustion problems occurring in one or more individual chambers 20. Specifically, if one combustion chamber is performing poorly, it is difficult to identify that chamber based on the exhaust gas flow and while the combustion section (and gas turbine) is operating. It would be useful to distinguish the combustion gases from one chamber from the gases of another chamber in order to diagnose problems in the combustion chambers.
A conventional technique for diagnosing combustion problems in a gas turbine is to shut down the gas turbine and physically inspect all of the combustion chambers. This inspection process is tedious and time-consuming. It requires that each of the combustion chambers be opened for inspection, even though most chambers are fine and require no maintenance. While this technique is effective in identifying problem combustion chambers, it is expensive in terms of lost power generation and of expensive repair costs. The power generation loss due to an unscheduled shut down of a gas turbine, especially those used in power generation utilities, is also costly and is to be avoided if at all possible. In addition, gas turbine shut-downs for combustion problems are generally lengthy because the problem is diagnosed after the gas turbine is shut down, cooled to a safe temperature and all chambers are inspected. There is a further delay in effecting repairs to obtain repair parts to fix the problem once the combustion problem is identified. Accordingly, combustion problems can force gas turbines to shut down for lengthy repairs.
There is a long-felt and unmet need for a reliable and accurate technique for identifying problem combustion chambers. Such a system would be preferably performed while the gas turbine is operating. Diagnosing a problem in a running combustion chamber would allow maintenance personnel to determine whether the gas turbine requires immediate shut-down, or if the repair may be delayed until the next scheduled maintenance shut-down. In addition, early diagnosis of combustion chamber problems would allow maintenance personnel to order repair parts prior to shut down, so that the parts are on hand when the combustion chamber is opened for repair. Repair of combustion chambers would be implemented quickly because the conventional delay of waiting for repair parts while the gas turbine is shut down is avoided. The present invention satisfies these needs.
The present invention provides an analytical tool for quickly and accurately identifying combustion chamber problems in an operating gas turbine. A combustion chamber graphic analyzer (CCGA) software application has been developed that identifies problem combustion chambers (or a problem area within a single annular chamber) within an operating gas turbine. The CCGA collects data regarding the operation of a gas turbine, including the temperature of exhaust gases from the gas turbine. This data is analyzed by the CCGA to determine the relative performance of each combustion chamber. The CCGA produces reports, e.g., charts, that identify combustion chambers that are experiencing potential problems, such as abnormally hot or cold combustion reactions. Based on the relative performance of each chamber, service personnel can identify malfunctioning combustion chambers and take appropriate corrective action.
The CCGA may generate a chart or other graphical display showing the relative temperature distribution of each combustion chamber, such as by identifying which combustion chambers have relatively xe2x80x9chotxe2x80x9d combustion temperatures and which chambers have relatively xe2x80x9ccoldxe2x80x9d combustion temperatures. By reviewing this chart, service personnel may quickly determine whether one or more combustion chambers are operating excessively hot or cold and, thereby, identify chambers having operating difficulties. This determination is made while the gas turbine is operating.
The software application for the CCGA may run on a standard computer, e.g., personal computer, and may be implemented using an off-the-shelf spreadsheet program, such as Microsoft Excel(trademark). A spreadsheet is used to implement the algorithms needed to convert operating data, such as turbine exhaust thermocouple array data, into a chart showing of the temperature distribution of the exhaust gases. In addition, linear algorithms for identifying excessive temperature differences within a combustion section may also be implemented in a spreadsheet program. An advantage of using a known spreadsheet software application as a platform on which to implement the CCGA algorithms is that the CCGA may run on many different types of computers, including personal and lap-top computers which are easily transported to individual gas turbines for analysis.
The CCGA system reduces the shut-down period during which a gas turbine is unavailable for producing power. The CCGA also reduces the instances in which gas turbines are shut down due to misdiagnosed combustion problems, and reduces the time required to repair the combustion problems when the gas turbine is shut down. Moreover, the CCGA identifies problem combustion chambers and avoids the prior need to inspect all chambers. Only problem chambers need to be opened and the other chambers can remain closed. By reducing the instances in which each chamber is inspected, fewer consumable parts, such as gaskets, are used during each inspection of the combustion section. Reducing the frequency of inspections of each chamber also minimizes the potential for damaging combustion parts during each inspection. Accordingly, the invention may reduce the cost and time needed to repair combustion chambers.
The CCGA system provides a reliable and quick analytical tool to determine the performance of the chambers in a combustion section of a gas turbine. The CCGA further provides an analytical tool that enables gas turbine service personnel to determine whether combustion chambers are operating with difficulties and whether those difficulties require the gas turbine to be shut down.